Nozzle shut off for injection molding system

ABSTRACT

An injection molding apparatus and method of fabricating a molded part are provided. The apparatus may include a barrel, a nozzle enclosing an end of the barrel and defining an opening in fluid communication with an inside of the barrel, and an extrusion screw positioned at least partially inside the barrel and rotatable relative to the barrel. The extrusion screw may include a screw tip. Relative axial movement between the barrel and the extrusion screw may open or close the opening of the nozzle to permit or prevent, respectively, material flow through the opening of the nozzle. The method may include clamping a mold, opening a nozzle, rotating the extrusion screw to pump a molten material into the mold until the mold is filled, closing the nozzle, and unclamping the mold to release a molded part.

CROSS-REFERENCES TO RELATED PATENT APPLICATIONS

This patent application is a continuation of U.S. patent applicationSer. No. 14/960,115, entitled “Nozzle Shut Off for Injection MoldingSystem”, and filed on Dec. 4, 2015, which claims the benefit under 35U.S.C. 119(e) of U.S. Provisional Patent Application No. 62/087,414,entitled “Extrude-to-Fill Injection Molding and Extrusion Screw,” andfiled on Dec. 4, 2014, U.S. Provisional Patent Application No.62/087,449, entitled “Nozzle Shut-off for Extrude-to-Fill InjectionMolding System,” and filed on Dec. 4, 2014, and U.S. Provisional PatentApplication No. 62/087,480, entitled “Control System for Extrude-to-FillInjection Molding,” and filed on Dec. 4, 2014, each of which is herebyincorporated herein by reference in its entirety.

FIELD

The present disclosure is directed to an injection molding system. Morespecifically, the present disclosure is directed to an injection moldingsystem including a nozzle closure apparatus. For example, the injectionmolding system may include an extrusion screw tip configured to shut offor close a nozzle.

BACKGROUND

A traditional injection molding system melts a material, such as aplastic, primarily by shear heat that is dynamically generated byrotation of a screw. The traditional injection molding system features abarrel with an opening at a hopper where plastic pellets enter thesystem and a nozzle where the plastic exits the barrel during injection.Between the hopper opening and the nozzle, the screw places pressure onthe plastic resin to generate shear heat, bringing the plastic melt tothe injection zone during a recovery extrusion stage of the moldingcycle. This shear heat generation system relies on the formation of acold slug in the nozzle to contain the plastic between each shot. Thecold slug seals the nozzle after the injection cycle and preventsadditional plastic from flowing out through the nozzle during therecovery extrusion stage that is between molding shots, trapping plasticin the barrel so that pressure can be applied to generate shear heat.However, the cold slug requires very high pressure to be dislodged toallow molten resin to flow out through the nozzle during the nextinjection cycle. The pressure applied to dislodge the cold slug islargely absorbed by the volume of plastic between the screw tip and thenozzle. Once the cold slug is dislodged, high pressure pushes the resinmelt into a mold cavity through a mold gate (e.g., an entrance to themold cavity) and runners or channels for delivering the melt into themold cavity. It is common for a traditional injection molding system tohave an injection pressure between 20,000 and 30,000 psi in order toobtain a pressure of 500-1500 psi in the mold cavity. Due to the highpressure, the traditional injection molding system typically includes abarrel having a heavy or thick wall section, which reduces the heatconduction to the plastic from the band heaters that surround thebarrel. The cold slug causes one of the greatest inefficiencies for thetraditional injection molding system.

Documents that may be related to the present disclosure in that theyinclude various injection molding systems include U.S. Pat. No.7,906,048, U.S. Pat. No. 7,172,333, U.S. Pat. No. 2,734,226, U.S. Pat.No. 4,154,536, U.S. Pat. No. 6,059,556, and U.S. Pat. No. 7,291,297.These proposals, however, may be improved.

There still remains a need to resolve the issues of the presentinjection molding systems to develop an automated and more efficientsystem that may provide additional flexibility for various applications.

BRIEF SUMMARY

The present disclosure generally provides an injection molding system,which may be referred to herein as an extrude-to-fill (ETF) injectionmolding apparatus, machine, or system. The injection molding systemgenerally includes a nozzle closure apparatus. The nozzle closureapparatus may include a screw tip that opens and closes a nozzle. Byusing the screw tip to open and close the nozzle, the cold slug in thetraditional injection molding system is eliminated, which allows theinjection molding system to operate at a lower injection pressure. Thelower injection pressure permits the thickness of the barrel to bereduced, which results in more effective conductive heating thatcontributes most of the heat needed for melting materials in the barrel.

In an embodiment, an extrude-to-fill injection molding apparatus isprovided. The apparatus may include an extrusion screw inside a barrel,a nozzle having a tip portion configured to enclose the screw tip, abarrel connection configured to connect to the barrel, and a middleportion between the tip portion and the barrel connection. The tipportion of the nozzle may have an opening for injecting moldingmaterial. The apparatus may include a screw tip coupled to the extrusionscrew. The screw tip may be configured to fit inside the tip portion ofthe nozzle to move along an axial direction inside the nozzle to sealand open the nozzle. The apparatus may include a hopper coupled to thebarrel and configured to fill a material into the barrel, and one ormore heaters placed outside the barrel.

In an embodiment, a method is provided for fabricating a plasticcomponent by an extrude-to-fill injection molding apparatus which mayinclude a hopper, an extrusion screw with a screw tip, a nozzle, one ormore heaters, and a motor. The method may include clamping a mold andactivating the motor to rotate the extrusion screw to move the screw tipaway from the nozzle, which opens the nozzle. The method may includerotating the extrusion screw to pump a molten material into the molduntil the mold is filled. The method may include reversing rotation ofthe extrusion screw to move the screw tip to close the nozzle, andcooling the mold to solidify the molten material in the mold. The methodmay include unclamping the mold to release a molded part.

In some embodiments, the screw tip may be a separate component from theextrusion screw. In some embodiments, the screw tip may be integratedwith the extrusion screw.

In some embodiments, a nozzle may be a component affixed to the barrel.In some embodiments, the nozzle may be integrated into the injectionmold and referred to herein as a nozzle insert.

In an embodiment, an injection molding apparatus is provided. Theinjection molding apparatus may include a barrel, a nozzle attached tothe barrel and defining an opening in fluid communication with an insideof the barrel, and an extrusion screw positioned at least partiallyinside the barrel and rotatable relative to the barrel. The extrusionscrew may include a screw tip. Relative axial movement between thebarrel and the extrusion screw may open or close the opening of thenozzle to permit or prevent, respectively, material flow through theopening of the nozzle.

In an embodiment, a method of fabricating a molded part is provided. Themethod may include clamping a mold, opening a nozzle by separating a tipof an extrusion screw from an opening formed in the nozzle, rotating theextrusion screw to pump a molten material into the mold until the moldis filled, closing the nozzle by positioning the tip of the extrusionscrew in sealed engagement with the nozzle, and unclamping the mold torelease the molded part.

Additional embodiments and features are set forth in part in thedescription that follows, and will become apparent to those skilled inthe art upon examination of the specification or may be learned by thepractice of the disclosed subject matter. A further understanding of thenature and advantages of the present disclosure may be realized byreference to the remaining portions of the specification and thedrawings, which forms a part of this disclosure.

The present disclosure is provided to aid understanding, and one ofskill in the art will understand that each of the various aspects andfeatures of the disclosure may advantageously be used separately in someinstances, or in combination with other aspects and features of thedisclosure in other instances. Accordingly, while the disclosure ispresented in terms of embodiments, it should be appreciated thatindividual aspects of any embodiment can be claimed separately or incombination with aspects and features of that embodiment or any otherembodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

The description will be more fully understood with reference to thefollowing figures and data graphs, which are presented as variousembodiments of the disclosure and should not be construed as a completerecitation of the scope of the disclosure, wherein:

FIG. 1 is a sectional view of an extrusion-to-fill (ETF) injectionmolding system with a screw tip for shutting off or closing a nozzlethat fits into a mold in accordance with embodiments of the presentdisclosure.

FIG. 2 is a perspective view of a screw tip of an ETF injection moldingsystem in accordance with embodiments of the present disclosure.

FIG. 3A is a front perspective view of a nozzle in accordance withembodiments of the present disclosure.

FIG. 3B is a front view of the nozzle of FIG. 3A.

FIG. 3C is a back perspective view of the nozzle of FIG. 3A.

FIG. 4 is a sectional view of the screw tip of FIG. 2 shutting off orclosing the nozzle of FIGS. 3A-3C in accordance with embodiments of thepresent disclosure.

FIG. 5 is a perspective view of a nozzle prior to assembly in accordancewith embodiments of the present disclosure.

FIG. 6 is a sectional view of the assembled screw tip of FIG. 2 with thenozzle of FIG. 5.

FIG. 7A shows the nozzle in a closed position in accordance withembodiments of the present disclosure.

FIG. 7B shows the nozzle of FIG. 7A in an open position in accordancewith embodiments of the present disclosure.

FIG. 8 is a flow chart illustrating steps for molding a part by using anETF injection molding system in accordance with embodiments of thepresent disclosure.

DETAILED DESCRIPTION

The present disclosure may be understood by reference to the followingdetailed description, taken in conjunction with the drawings asdescribed below. It is noted that, for purposes of illustrative clarity,certain elements in various drawings may not be drawn to scale.

The present disclosure generally provides a screw tip configured to shutoff or close a nozzle for an injection molding apparatus, machine, orsystem, which may be referred to herein as an extrusion-to-fill (ETF)injection molding system. The screw tip aids in more efficient injectionfor the ETF injection molding system because there is no cold slug to bedislodged at high pressure like the traditional injection moldingsystem. The ETF injection molding system uses the screw tip to seal thenozzle between molding shots. The nozzle may be opened by separating atip of an extrusion screw from an opening formed in the nozzle, and thenozzle may be closed by positioning the tip of the extrusion screw insealed engagement with the nozzle.

The injection molding system may utilize a screw including a screw tipwith geometry that matches a nozzle such that material flow isprohibited when the screw tip engages the nozzle and material flowsfreely when the screw tip is disengaged from the nozzle. In someembodiments, the screw may be reciprocated between an open position inwhich the screw tip is disengaged from the nozzle and a closed positionin which the screw tip is engaged with the nozzle. Rotation of the screwmay change its axial position to open and close the nozzle. In otherwords, a single cylinder or motor may move the screw and advance thescrew tip into and out of engagement with the nozzle to prevent orpermit, respectively, flow of material into a cavity defined by a mold.In some embodiments, the screw is rotatable but is fixed in an axialdirection. In these embodiments, a barrel in which the screw ispositioned may be moveable in an axial direction relative to the screw.The nozzle may be attached to the barrel such that movement of thebarrel towards the mold seals the nozzle against the mold sprue orinlet, and this movement of the barrel opens the nozzle and permitsmaterial to flow from inside the barrel into a mold cavity. The barrelmay apply pressure to the nozzle to seal the interface between thenozzle and the mold sprue or inlet. In these embodiments, a motor may beattached to the screw to rotate the screw and a cylinder may be attachedto the barrel to move the barrel fore and aft to move the nozzle intoand out of contact with the mold sprue or inlet.

The ETF injection molding system facilitates the use of static heatconduction to melt material, such as plastic, as the injection moldingsystem uses lower pressure because there is no cold slug formed betweenmolding shots, which allows for a thinner wall of the barrel. By usingstatic heat conduction to melt material, and the screw tip to seal thenozzle without any cold slug formed between molding shots, the injectionmolding system may extrude intermittently and on demand under asignificantly lower pressure than the traditional injection moldingsystem. Resistance to material flow is a function of the materialviscosity, and the static heat conduction of the injection moldingsystem assures a consistent and controlled material temperature andviscosity. In some embodiments, the injection molding system maygenerate the same pressure as the pressure in the mold cavity or aslightly higher injection pressure, such as 5-10% higher injectionpressure, than the pressure in the mold cavity. In some moldapplications, the injection molding system may require an injectionpressure of only 500 psi to 1500 psi to fill a mold. The temperature andviscosity consistency may result in more uniformly molded part densityas well as less warping and part deformation post molding. Generally, ahigher injection molding pressure of between 20,000 and 30,000 psi, forexample, is required in the traditional system due to non-uniformtemperature and viscosity resulting from shear heat generation, and theneed to remove the cold slug. This may result in higher densityvariation and part deformation in molded parts. A large pressuredifference in the traditional system may be present between regions nearthe nozzle and inside the mold cavity and thus may produce parts of lessuniformity.

FIG. 1 is a sectional view of an injection molding system, referred toherein as an ETF injection molding apparatus, machine, or system, with ascrew tip 102 that is operable to shut off or close a nozzle 108 thatfits into a mold 112 in accordance with embodiments of the presentdisclosure. In FIG. 1, the screw tip 102 is in an open position to letmaterial flow into a mold cavity defined by the mold 112. In the openposition of FIG. 1, the screw tip 102 is spaced apart from the nozzle108 to allow material 116, which may be referred to herein as a resinmelt, to flow through an opening 114 formed in the nozzle 108.

In the example illustrated in FIG. 1, the nozzle 108 is formed as anozzle insert, which fits to the mold 112. In FIG. 1, the nozzle 108 isreceived at least partially in an entrance or inlet of the mold 112 andengages the mold 112 in a sealed engagement. The nozzle 108 may includea peripheral flange that abuts against the mold 112 when the nozzle 108is fully inserted into the entrance or inlet defined by the mold 112.The flange may contribute to the sealed engagement between the nozzle108 and the mold 112. Referring still to FIG. 1, the opening 114 isformed in the nozzle 108 and provides a passage for injecting thematerial 116 from within a barrel 106 of the injection molding systeminto a mold cavity defined by the mold 112. As illustrated in FIG. 1,when the screw tip 102 is spaced apart from the nozzle 108, a resin melt116 may flow around the screw tip 102, through the opening 114 of thenozzle 108, and into the mold cavity defined by the mold 112. As furtherdiscussed below, flow of the resin melt 116 may be caused by rotation ofan extrusion screw 104.

With continued reference to FIG. 1, the extrusion screw 104 may bepositioned inside the barrel 106. The extrusion screw 104 may includethe screw tip 102, which is configured or shaped to match the geometryof the nozzle 108 near the opening 114. The extrusion screw 104 isplaced inside the barrel 106 and may rotate inside the barrel 106 in twodirections, e.g. clockwise and counter-clockwise. In some embodiments,the extrusion screw 104 may move axially along axis 118 forward towardthe opening 114 and move axially backward away from the opening 114 ofthe nozzle 108. As illustrated in FIG. 1, the end 122 of the barrel 106may fit inside the nozzle 108. In the illustrated embodiment, a heater110 is attached to the outer surface of the barrel 106. In thisembodiment, the heater 110 is outside the mold 112. In some embodiments,the heater may extend to the end 122 of the barrel 106 and may fitinside the nozzle 108 (see FIG. 6).

As shown in FIG.1, the screw tip 102 is spaced from the nozzle 108 at adistance from the opening 114 of the nozzle 108, which is an openposition to allow the material 116 to flow into a cavity defined by themold 112 through the opening 114. The screw tip 102 of the illustratedembodiment includes an angled transition portion to help material flow.The angled transition portion may be formed at an angle α, identified byarrows 120 in FIG. 1, relative to a longitudinal axis of the extrusionscrew 104, such as the axis 118. The angle α may vary depending on themold application. In some embodiments, the angle α may be between 15°and 45°. Smaller angles may help the material 116 flow better, but wouldincrease the length of the angled portion of the screw tip 102.Preferably, the angle α may be between 20° and 40°, and more preferablybetween 25° and 35°.

The screw tip 102 may extend axially into the nozzle 108 and fitprecisely inside the nozzle 108 to seal the nozzle 108 and close theopening 114, thereby restricting the material 116 from flowing throughthe opening 114. In some embodiments, the screw tip 102 moves along theaxis 118 toward the opening 114. The screw tip 102 can seal the opening114 of the nozzle 108 to prevent additional resin melt 116 from enteringthe mold 112. The screw tip 102 may displace the resin melt 116 thatwould normally form a cold slug prior to the recovery extrusion stage ofthe traditional injection molding process.

As an example for the dimension of the screw tip, the screw tip 102 maymove away at a distance from the nozzle to allow material flow into themold cavity of the mold 112. For example, the distance may be about 0.25inches. The opening may be proportional to the screw root diameter. Theopening 114 may be 0.25 inches in diameter, while the extrusion screw104 may have an inner diameter 124 of 0.5 inches. The barrel 106 mayhave an inner diameter of 0.75 inches and an outer diameter of 1.0inches. The angle α of the tip from the axial direction may be about30°. It will be appreciated by those skilled in the art that thedimensions and shapes of the nozzle insert, barrel, and screw may vary.

A support, such as a cylinder (not shown), may be placed at a back endof the extrusion screw 104, opposite to a front end where the screw tip102 is located. When an injection cycle begins, the support may bereleased from the back end of the extrusion screw 104 to allow theextrusion screw 104 to move backward. When the extrusion screw 104begins to rotate, the screw tip 102 may immediately move backwardaxially to open the nozzle 108 such that the resin melt 116 can beinjected or pumped into the mold 112 through opening 114.

When the injection cycle is completed, e.g. the mold 112 is filled, theextrusion screw 104 reverses its rotation to move the screw 104 forwardaxially until the screw tip 102 closes or shuts off the nozzle 108. Thesupport or cylinder may be activated to move forward during the screwreversal to ensure the shut-off or seal of the nozzle 108.

In addition or alternative to axial movement of the screw tip 102relative to the nozzle 108 to open or close the opening 114 of thenozzle 108, the nozzle 108 may be moved axially relative to the screwtip 102 to open or close the opening 114 of the nozzle 108. In someembodiments, the barrel 106 is attached to the nozzle 108 and the barrel106 is axially moveable along the axis 118 relative to the screw tip102, thereby causing the nozzle 108 to move relative to the screw tip102. From a closed position, the barrel 102 may be moved forwardrelative to the screw tip 102, causing the nozzle 108 to move away fromthe screw tip 102 and open the opening 114 of the nozzle 108 to allowmaterial 116 to flow through the opening 114 and into a cavity definedby the mold 112. From this open position, the barrel 102 may be movedrearward relative to the screw tip 102, causing the nozzle 108 to moveinto engagement with the screw tip 102 and close the opening 114 of thenozzle 108 to prevent material 116 from flowing through the opening 114.The barrel 106 may be operably coupled to a cylinder that moves thebarrel 106 between open and closed positions and asserts pressure on thebarrel 106 to seal the nozzle 108 against the mold 112 when the barrel106 is in the open position. The cylinder may reciprocate the barrel106, and thus the nozzle 108, between the open and closed positions. Insome embodiments, the screw 104 is fixed axially, and the screw 104rotates within the barrel 106 when the barrel 106 is in the openposition to pump the material 116 through the opening 114 of the nozzle108 into a cavity defined by the mold 112.

In some embodiments, the screw tip 102 may be a separate component fromthe extrusion screw 104. FIG. 2 is a perspective view of the screw tipin accordance with embodiments of the present disclosure. As shown, ascrew tip 200 includes a screw tip portion 202 that matches to theopening 114 of the nozzle 108. The screw tip portion 202 may be in aform of a disk or a plate of any shape, including circular, square,rectangular, and oval, among others. The screw tip 200 may include anon-threaded cylindrical portion 206. The screw tip 200 may include anangled transition portion 204 connecting the screw tip portion 202 tothe cylindrical portion 206. The angled transition portion 204 may havean angle β between 15° and 45°. Smaller angles may help the materialflow better, but increase the tip dimension. Preferably, the angle β maybe between 20° and 40°, more preferably between 25° and 35°.

The screw tip 200 may be attached to the extrusion screw 104 in variousmanners, including a threaded engagement, a pinned engagement, or asnap-fit engagement, among others. As an example, the screw tip 200 mayinclude a threaded cylindrical portion 210 with outer threads matched toinner threads of the extrusion screw 104 near the end of the screw 104,such that the screw tip 200 can be attached to the end of the extrusionscrew 104. The screw tip 200 may include a middle flange portion 208between the non-threaded cylindrical portion 206 and the threadedcylindrical portion 210. The middle flange portion 208 may extendradially from the non-threaded cylindrical portion 206 and the threadedcylindrical portion 210 to position the screw tip 200 properly onto theextrusion screw 104.

The screw tip 200 may be configured to fit into a nozzle 300 as shown inFIGS. 3A-3C. FIG. 3A is a front perspective view of a nozzle inaccordance with embodiments of the present disclosure. FIG. 3B is afront view of the nozzle of FIG. 3A. FIG. 3C is a back perspective viewof the nozzle of FIG. 3A. The nozzle 300 may include a nozzle tipportion 306 with an opening 302, which allows a material to be injectedinto a mold. The opening 302 may be in a circular shape as shown or anyother shape.

The nozzle 300 may be attached to a barrel (e.g., barrel 402 in FIG. 4)in various manners, including a threaded engagement, a pinnedengagement, a snap-fit engagement, among others. As an example, thenozzle 300 may include a threaded barrel portion 304 with outer threadsmatched to inner threads of a barrel near an end of the barrel, suchthat the nozzle 300 may be attached to the end of the barrel (e.g.,barrel 402 in FIG. 4). The nozzle 300 may include a flange portion 308connecting, and positioned between, the tip portion 306 and the threadedbarrel portion 304. The flange portion 308 and the tip portion 306 maybe configured to fit into a mold.

FIG. 4 is a sectional view of the screw tip 200 of FIG. 2 shutting offor closing the nozzle 300 of FIGS. 3A-3C in accordance with embodimentsof the present disclosure. FIG. 4 shows that the screw tip is placed ata position to close the opening 302 of the nozzle 300. As shown, one endof the screw tip 200 is attached to the extrusion screw 404 by fasteningthe outer threads of the threaded cylindrical portion 210 of the screwtip 200 to the inner threads 410 of the extrusion screw 404 at an end ofthe screw 404. In the illustrated embodiment, the middle flange portion208 of the screw tip 200 is abutted against the end of the extrusionscrew 404.

The screw tip portion 202 may be shaped to match the geometry of theopening 302 while the transition portion 204 of the screw tip 200 may beshaped to match the geometry of the inner surface of the side wall ofthe nozzle tip portion 306, such that the screw tip 200 can seal theopening 302 of the nozzle 300. As shown in FIG. 4, the resin melt 116 ispushed away from the opening 302 of the nozzle 300 by the tip portion202 and the transition portion 204 of the screw tip 200.

Referring still to FIG. 4, the nozzle 300 may be attached to an end ofthe barrel 402 in various manners. For example, the nozzle 300 may beattached to an end of the barrel 402 by fastening the outer threads ofthe threaded portion 304 of the nozzle 300 to the inner threads 406 ofthe barrel 402 near the end of the barrel 402. The flange portion 308 ofthe nozzle 300 is against the end of the barrel 402.

As illustrated in FIG. 4, a small clearance 412 may exist between thebarrel 402 and the extrusion screw 404. The clearance 412 may facilitatethe extrusion screw 404 to rotate freely within the barrel 402. Theclearance 412 may be large enough to largely or substantially preventmaterial 116 from being sheared between the barrel 402 and the extrusionscrew 404.

In some embodiments, the extrusion screw 404 may rotate and movebackward a small axial distance to open the nozzle 300. The extrusionscrew 404 may rotate reversely to move forward the small axial distanceto close or shut off the nozzle 300 when the extrusion cycle is haltedby the mold 112 being filled of material, such as a plastic or any othermaterial. In addition or alternative to axial movement of the extrusionscrew 404, the barrel 402 may move forward an axial distance relative tothe screw 404 to open the nozzle 300 and may move backward or rearwardan axial distance relative to the screw 404 to close the nozzle 300.

With continued reference to FIG. 4, band heaters 110, such as electricalheaters, may be placed outside the barrel 402 to heat the material orresin 116. The extrusion screw 404 may be hollow inside, such that aresistor heater 408 or other heat source may be placed inside theextrusion screw 404 to further heat the resin 116. The extrusion screw404 may be formed of a highly conductive material, like brass, toenhance the heat conduction.

In some embodiments, inductive heat conduction may be possible by usinga magnetic barrel or magnetic screw. Induction heat generators may beused to facilitate quicker response time than electric heaters. Forexample, the ETF injection system may use an induction heat generatoralong with a magnetic barrel section and/or a magnetic screw toinstantly heat the barrel and the extrusion screw. In some embodiments,the barrel and/or extrusion screw may include at least a magneticportion or section to further facilitate quicker response time.

The ETF injection molding system is less sensitive to material puritylevel, material cleanliness, contaminants, resin grades, or unknownsources than the traditional system. The materials for molding mayinclude any amorphous thermoplastics, crystalline and semi-crystallinethermoplastics, virgin resins, fiber reinforced plastics, recycledthermoplastics, post-industrial recycled resins, post-consumer recycledresins, mixed and comingled thermoplastic resins, organic resins,organic food compounds, carbohydrate based resins, sugar-basedcompounds, gelatin//propylene glycol compounds, starch based compounds,and metal injection molding (MIM) feedstocks, among others. The materialmay be in form of pellets, flakes, or any irregular shapes. For example,mixed and comingled thermoplastic scrap materials that currently wouldbe disposed of as landfill waste may be used for the ETF injectionmolding.

The nozzle fits between a mold and a barrel for injection molding. Insome embodiments, the nozzle may be a single component or piece as shownin FIG. 1. In some embodiments, the nozzle may be an assembled part froma few individual components, because it may be easier to fabricate theindividual components. The nozzle may be formed from various materials.In some embodiments, the nozzle is formed from a metal.

FIG. 5 is a perspective view of a nozzle prior to assembly in accordancewith embodiments of the present disclosure. A nozzle 500, which may beintegrated into a mold and referred to herein as a nozzle insert, mayinclude a mold gate 504, which is an entrance for injecting the materialinto a mold. The mold gate 504 may be formed in a barrel shape having afirst barrel portion 510 with a smaller diameter than a second barrelportion 512. The nozzle 500 may include a mold thread 506, which may bereferred to herein as a mold insert. The mold thread 506 may enclose themold gate 504 and may be attached to the mold.

The nozzle 500 may include a mold core or mold core assembly 502, whichmay be formed in a barrel or tubular shape with various portions ofdifferent inner and outer dimensions. The mold core assembly 502 mayenclose the mold gate 504 and may be positioned between the mold gate504 and the mold thread 506, as illustrated in FIG. 6.

The mold core assembly 502 may include a first end portion 514 that hasan inner diameter larger than the outer diameter of the mold gate 504and an outer diameter smaller than the inner diameter of the mold thread506. As illustrated in FIG. 6, the mold thread 506 may be placed outsideor surround the first end portion 514 of the mold core assembly 502. Themold thread 506 may be configured to attach to a mold. As illustrated inFIG. 6, the mold gate 504 may be placed inside the mold core assembly502.

The mold core assembly 502 may include a second end portion 520 with alarger outer dimension or diameter, such that the second end portion 520may act as a stopper when the nozzle 500 is placed into the mold. Thesecond end portion 520 may be placed against the mold for molding.

The mold core assembly 502 may include a first middle transition portion516 that has an inner diameter close to the outer diameter of the secondbarrel portion 512 of the mold gate 504 to surround the mold gate 504.As illustrated in FIG. 6, the first barrel portion 510 of the mold gate504 may be positioned inside the first end portion 514 of the mold coreassembly 502, and the second barrel portion 512 of the mold gate 504 maybe positioned inside the first middle transition portion 516 of the moldcore assembly 502. The second barrel portion 512 of the mold gate 504may abut against the first end portion 514 of the mold core assembly 502when the mold gate 504 is seated inside the mold core assembly 502. Asillustrated in FIG. 6, the mold thread 508 may be surround the first endportion 514 of the mold core assembly 502 and may abut against the firstmiddle transition portion 516 of the mold core assembly 502 when themold core assembly 502 is inserted into the mold thread 508. The firstmiddle transition portion 516 may have an angled outer surface to form asmooth transition from the mold thread 508 to a second middle transitionportion 518 of the mold core assembly 502.

In some embodiments, the screw tip 102 may be integrated with theextrusion screw 104 as a single component. FIG. 6 is a sectional view ofthe assembled screw tip of FIG. 2 and the nozzle 500 of FIG. 5 sealed bythe screw tip. In the embodiment illustrated in FIG. 6, the screw tip isnot a separate component from the extrusion screw 604, which isdifferent from the embodiment in FIG. 4. The extrusion screw 604 may bea solid piece such that the extrusion screw 604 does not contain aheater inside the extrusion screw 604, which is an alternativeembodiment from that shown in FIG. 4.

As shown in FIG. 6, the first barrel portion 510 of the mold gate 504may be configured to enclose a tip portion 608 of the extrusion screw604 inside a barrel 602. The second barrel portion 512 of the mold gate504 may have a larger dimension than the first barrel portion 510 topartially enclose the extrusion screw 604.

The mold core assembly 502 may enclose a heater 606 outside the barrel602 as shown in FIG. 6, which is different from the embodiment shown inFIG. 1. The second end portion 520 of the mold core assembly 502 mayhave an inner diameter larger than the band heater 606 to enclose theband heater 606. The second middle transition portion 518 of the moldcore assembly 502 may have a larger inner dimension or diameter than thefirst middle transition portion 516 of the mold core assembly 502 toenclose the heater 602.

FIG. 7A shows the nozzle 708 in a closed position 700A in which thescrew tip 712 closes or shuts off the nozzle 708. As previouslydiscussed, to close the nozzle 708, the extrusion screw 702 may be movedforward toward the nozzle 708. When the screw 702 moves forward, thescrew tip 712 fits into the side wall of the nozzle 708, which seals themolten material from flowing into the mold and also prevents theformation of a cold slug. Alternatively, to close the nozzle 708, thebarrel 710 may be moved rearward relative to the screw 702, causing thenozzle 708 which is attached to the barrel 710 to move towards the screwtip 712 and engage the screw tip 712 to seal the molten material fromflowing through the nozzle 708.

FIG. 7B shows the nozzle 708 in an open position 700B. As previouslydiscussed, to open the nozzle 708, the extrusion screw 702 may be movedbackward away from the nozzle 708. A support (not shown), such as asmall cylinder behind the extrusion screw 702, may be released wheninjection molding commences. When the extrusion screw 702 initiallyrotates to advance material inside a barrel 710, the screw tip 712 maymove backward a small distance from the nozzle 708, thereby opening thenozzle 708. With the nozzle 708 in the open position 700B, the extrusionscrew 702 rotates within the barrel 710 to pump the material into themold until the mold is filled. In other words, the shot size is notlimited by a fixed stroke like in traditional injection molding systems.The present ETF injection system can extrude plastic continuously tofill a mold cavity of any size.

When the mold cavity is filled, the screw rotation may be reversed tomove the screw 702 forward to place the screw tip 712 against the nozzle708, which decompresses the barrel 710 and the material within thebarrel 710. Simultaneously, a cylinder associated with the screw 702 mayapply pressure to the back of the extrusion screw 702 to assure that thescrew tip 712 seats properly inside the nozzle 708. Alternatively, toopen the nozzle 708, the barrel 710 may be moved forward relative to thescrew 702, causing the nozzle 708 to move away from and disengage thescrew tip 712, and thereby permitting molten material to flow frominside the barrel 710, through the nozzle 708, and into a mold againstwhich the nozzle 708 is placed.

To prepare for molding a part by using the ETF injection molding system,the extrusion screw and/or the barrel may be moved to place the nozzleagainst a gate of a mold. The hopper may be filled with a material to bemolded. The material may be in forms of pellets or flakes or anyirregular shapes. The hopper may be cooled by water or other coolants.One or more heaters may be turned on to melt the material as it isfilled in the barrel from the hopper. The material is between the innersurface of the barrel and the outer surface of the extrusion screw asshown in FIGS. 1 and 6.

FIG. 8 is a flow chart illustrating steps for molding a part by using anETF injection molding system in accordance with embodiments of thepresent disclosure. Method 800 may include clamping a mold at operation802. The clamping may be achieved in various manners, which may include,but are not limited to, applying a pneumatic clamping force (e.g., anair pressure based actuation system), a mechanical clamping force (e.g.,a mechanical clamp), and/or an electrical clamping force (e.g., aservomotor-based actuation system) at operation 802. In embodimentsusing air pressure, the air pressure may vary depending on the size ofthe mold. In some embodiments, the injection molding system may generatethe same pressure as the pressure in the mold cavity or a slightlyhigher injection pressure, such as 5-10% higher injection pressure, thanthe pressure in the mold cavity. In some embodiments, the air pressuremay range from 90 psi to 110 psi. The mold may be formed of variousmaterials, including a metal such as aluminum or steel. Because of thelow pressure used in the extrusion, an aluminum mold can be used for theETF injection molding system. For the traditional injection moldingsystem, steel molds are typically used due to the high pressure requiredfor extrusion.

Method 800 continues with activating a motor to rotate the extrusionscrew to open the nozzle at operation 806. Alternatively, as previouslydiscussed, the nozzle may be opened by moving the barrel relative to thescrew. The motor may be coupled to an end of the extrusion screw torotate the extrusion screw in one direction, either clockwise orcounter-clockwise, depending upon the screw design. Method 800 mayinclude rotating the extrusion screw to pump a molten material into themold at operation 810. When the mold is filled, the motor may reversethe screw rotation to move the screw tip forward to close the nozzle atoperation 814. Alternatively, as previously discussed, the nozzle may beclosed by moving the barrel relative to the screw. The molten materialmay take time to cool in the mold at operation 818. The time may vary,such as cooling within a few seconds for example. After cooling, themold may be unclamped such that a part can be released at operation 822.The mold may be unclamped in various manners, which may includereleasing an air pressure applied to the mold.

Having described several embodiments, it will be recognized by thoseskilled in the art that various modifications, alternativeconstructions, and equivalents may be used without departing from thespirit of the invention. Additionally, a number of well-known processesand elements have not been described in order to avoid unnecessarilyobscuring the present invention. Accordingly, the above descriptionshould not be taken as limiting the scope of the invention. All of thefeatures disclosed can be used separately or in various combinationswith each other.

Those skilled in the art will appreciate that the presently disclosedembodiments teach by way of example and not by limitation. Therefore,the matter contained in the above description or shown in theaccompanying drawings should be interpreted as illustrative and not in alimiting sense. The following claims are intended to cover all genericand specific features described herein, as well as all statements of thescope of the present method and system, which, as a matter of language,might be said to fall there between.

1. A method of molding a part, comprising: rotating a screw within abarrel to extrude a molten material through a nozzle opening of a nozzleinto a mold cavity; and after extruding the molten material through thenozzle opening, inserting a cylindrical tip portion of the screwcorresponding in geometry to the nozzle opening into the nozzle openingalong an entire axial length of the nozzle opening to displace all ofthe molten material from the nozzle opening.
 2. The method of claim 1,wherein inserting the tip portion of the screw into the nozzle openingcomprises inserting the tip portion of the screw into the nozzle openinguntil the tip portion of the screw is substantially flush with anexterior surface of the nozzle.
 3. The method of claim 1, whereininserting the tip portion of the screw into the nozzle opening comprisessealingly engaging the tip portion of the screw with the nozzle alongthe entire axial length of the nozzle opening.
 4. The method of claim 1,further comprising sealingly engaging an interior surface of the nozzlewith a transition portion of the screw.
 5. The method of claim 4,wherein the transition portion of the screw extends outward from the tipportion of the screw.
 6. The method of claim 5, wherein the transitionportion of the screw extends rearward from the tip portion of the screw.7. The method of claim 4, wherein the tip portion of the screw has asmaller axial length than the transition portion of the screw.
 8. Themethod of claim 1, wherein rotating the screw within the barrel causesthe molten material to flow around the tip portion of the screw, throughthe nozzle opening, and into the mold cavity.
 9. A method of molding apart, comprising: injecting a molten material through a nozzle openingof a nozzle into a mold cavity; and after injecting the molten materialthrough the nozzle opening, inserting a cylindrical tip of a screwcorresponding in geometry to the nozzle opening into the nozzle openingalong an entire axial length of the nozzle opening to displace all ofthe molten material from the nozzle opening.
 10. The method of claim 9,wherein injecting the molten material through the nozzle openingcomprises rotating the screw within the barrel.
 11. The method of claim10, wherein rotating the screw within the barrel causes the moltenmaterial to flow around the tip of the screw, through the nozzleopening, and into the mold cavity.
 12. The method of claim 9, whereininserting the tip of the screw into the nozzle opening comprisesinserting the tip of the screw into the nozzle opening until the tip ofthe screw is substantially flush with an exterior surface of the nozzle.13. The method of claim 9, wherein inserting the tip of the screw intothe nozzle opening comprises inserting the tip of the screw through thenozzle opening such that the tip of the screw seals the nozzle openingalong the entire axial length of the nozzle opening.
 14. The method ofclaim 9, wherein inserting the tip of the screw into the nozzle openingcomprises sealingly engaging the tip of the screw with the nozzle alongthe entire axial length of the nozzle opening.
 15. The method of claim9, further comprising sealingly engaging an interior surface of thenozzle with a portion of the screw located rearward of the tip of thescrew.
 16. The method of claim 15, wherein the portion of the screwextends outward from the tip of the screw.
 17. The method of claim 15,wherein the tip of the screw has a smaller axial length than the portionof the screw.
 18. A method of molding a part, comprising: rotating ascrew within a barrel to pump a molten material through a cylindricalnozzle opening of a nozzle into a mold cavity; and after pumping themolten material through the nozzle opening, inserting a cylindrical tipof the screw corresponding in geometry to the nozzle opening into thenozzle opening along an entire axial length of the nozzle opening todisplace all of the molten material from the nozzle opening.
 19. Themethod of claim 18, wherein the tip of the screw is spaced apart fromthe nozzle opening while rotating the screw within the barrel to pumpthe molten material around the tip of the screw, through the nozzleopening, and into the mold cavity.
 20. The method of claim 18, whereininserting the tip of the screw into the nozzle opening comprisesinserting the tip of the screw into the nozzle opening until the tip ofthe screw is substantially flush with an exterior surface of the nozzle.